Assessing tunnel leakage potential is crucial in hydroelectric projects to ensure an adequate water supply for energy generation and to mitigate associated geotechnical risks. This study’s findings, which evaluate tunnel water leakage potential, considering the vertical and lateral covers and the characteristics of joints at the rock mass mapped during excavation, are of significant importance. The leakage potential has been identified along the tunnel alignment in areas with high water leakage risks. Numerical modeling was then conducted in regions with low overburden and lateral cover, particularly where high leakage potential was identified, using a valley model under in-situ stress (confinement) conditions to predict the likelihood of hydraulic jacking and water outflow from the tunnel toward the valley side. The manuscript finally highlights the necessity of adequate vertical and lateral cover to minimize leakage in general and assists in selecting locations for effective treatment measures. Additionally, the study further emphasizes the importance of providing the sufficient valley side cover in the design phase in case of pressurized water tunnel.